Project Summary/Abstract Metals are essential micronutrients that are required for proper functioning of cells and organisms. As such, cells have evolved a complex homeostatic machinery to control the distribution and speciation of metals, also known as the metallome. Deviations from basic metallomic profiles are associated with multiple disease processes, environmental metal contamination, and nutritional deficiencies and all have detrimental effects on normal cellular function. The metallome is comprised of two main metal ion pools including the labile metal ion pool in which metals are weakly bound to cellular ligands and the tightly-bound metal ion pool in which metals are ligated to metalloproteins and other biomolecules with high affinity. Metalloproteins that constitute the tightly-bound metal ion pool represent one third of the cellular proteome and within these proteins, metals have diverse structural and catalytic functions. These metalloproteins can exist in several states including apo (metal-free), holo (metal-bound), and mismetalated depending on the cellular context. While some information is know about how the metalation state of selected metalloproteins is controlled (via metallochaperones and/or action of specific metal transporters) the details of how the labile and metalloprotein-bound metal pools interact in a cellular context as cells undergo dynamic changes is largely unknown and is a growing area of interest in the metal homeostasis field. In order to probe these interactions and characterize how the pool of metalloproteins changes in physiology and pathology, our goal is to develop a diverse chemical toolbox that will enable imaging, identification, quantification, and molecular control of metalloprotein populations in cells, tissues, and organisms. Our strategy centers on the use of precisely design molecular targeting groups that will specifically interact with the metal sites of these proteins. These targeting groups are then modified with functional tags including the following: 1) Fluorophores for live cell imaging and cell lysate protein analysis; 2) Affinity probes for proteomics studies that enable trapping of metalloproteins in their native metallation state and; 3) Photoresponsive groups for the selective control of specific metalloproteins and the development of photopharmacophores. Initial studies have focused on zinc-dependent metalloenzymes including carbonic anhydrases; however studies will be expanded to include a range of enzymes dependent on zinc (e.g. metallo- ?-lactamases, histone deacetylases, matrix metalloproteinases), iron (e.g. heme and non-heme) and copper (e.g. superoxide dismutase). Tools will be applied in cellular models of metal dyshomeostasis and for profiling metalloprotein pools in cancer cells and others and will be combined with additional metallomic analysis including elemental analysis (inductively coupled plasma mass spectrometry, synchrotron-based x-ray fluorescence microscopy) and imaging of labile metal ion pools. Insights gained from the molecular tools furnished by these studies will contribute to the identification of metalloproteins of interest in cancer and other diseases and the development of therapeutic and diagnostic strategies to combat them.